I have been looking around at different google results for uvb light, and gotta say, there are so many people who 'think' things that aren't true. So, to put a few of these untrue thoughts to bed, I decided to make this thread.

First of all, neither High Pressure Sodium or Metal Halide will put out UVB light. It is true that Metal Halide will create it, but the glass is made to filter it out. Same with halogen's around that spectrum.
People are saying UVB is 280nm, also untrue, it is ~ 311nm. 280 is much lower than UVB.
I bought a coil, repti-glo 10.0, and returned it. The compact flourescent UVB bulbs are ok, but they will not cover a large amount of area, get tubes.
To get UVB, tanning lights or reptile lights are pretty much the only way.
Mercury Vapor, which produces more UVB, also has a glass housing which will keep UVB from going through, or at least dampen it greatly.

What you want is 10.0 (10%) uv-b tubes. About 2-4 inches is far enough away to be good for the plants, as the lamps themselves will put out somewhere in the vicinity of 400 microwatts/square cm.

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ya good pointing out the wavelength there Ive seen that as well.
I prefer CFL's with proper reflectors. In my experience, It is better to rotate these out--this is because it is better to have light that is proper intensity than it is to have it constant...tubes just disperse too much to be used IMO...
I get 10x better results with ~240uW/f2 every other day than ~150uW/f2 every day....better to rotate and keep intense than to just set up high and forget about them--I've got screw fittings all throughout my room, at all angles to hit all nugs. None of these uvb bulbs sit above a ganja/top cola--I keep them all "in the midst of" the plants.

UVB really is what makes the difference in primo nug, and to do it right, as much as anything else in growing, takes tlc (rotating bulbs, adjusting timers weekly)....

I hate moving CFLs... I use a 400w HPS and the way I have these fittings to where I can move the bulbs....in the midst of my plants.... has taken some effort out...

with tubes, the dispersion should help but I didn't think they were intense enough even close to the bulb.

Far be it from me tho if you're gettin 400uW/f2

Bottom line though I would put (proper) intensity above regularity when it comes to UVB, tho both are important. If you start at 6-8hours mid photoperiod beginning of flower (preferably late veg) and taper off just a lil every day to where you're an hour or less at harvest, that is how it is meant to be done. Any improvement on imitation of the sun's UVB photoperiod I would love to hear what others have had success with!!!!

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"Except for transmutation and turning lead into gold, there has been more nonsense written about seedless marijuana than on any other subject."

- Marijuana Optics